The present invention relates to a method for filling a trench that is formed in a production process of a semiconductor device. Particularly, the present invention relates to a method for filling the trench with a high aspect ratio by using a high density plasma (HDP) technique. Further, the present invention relates to the Shallow Trench Isolation (STI) technique with a high isolation resistance.
The minute isolation is required in the manufacturing of semiconductor devices, along with the shrink of the semiconductor device in recent years. STI has been used. And, the shrink of STI area is also being carried out for the same purpose. The width of the opening of the STI trench becomes narrow and the depth of it becomes deep. That is, the aspect ratio that is the ratio of the depth to the width of the opening increases. Thus, the process filling an insulator into the trench with high aspect ratio is needed in forming the STI area.
The silicon oxide (SiO2) film by HDP chemical vapor deposition (CVD) (hereinafter, this silicon oxide film is called an HDP film) is filled into the high aspect trench. However, the aspect ratio of the trench of STI area increases with the further shrink of the semiconductor device in recent years. A trench exceeding a high aspect ratio of 3 is not able to fill even by the HDP film. When the HDP film is filled into the trench on a silicon substrate, the upper part of the trench is closed with the HDP film. A void results within a trench. The trench cannot completely fill.
Also, the STI area, whose width is narrow and isolation performance is high, is required in the device that uses the high voltage such as EEPROM (electrically erasable programmable read only memory). The STI area, whose width is narrow and isolation performance is high, has a deep trench. The aspect ratio of the trench becomes very high in the STI area of the cell array of the EEPROM. The filling of the HDP film into the deep trench was difficult.